How to add Remote Event Receivers to SharePoint List through REST

Adding Event receivers to al List through REST: Msdn has page about REST calls to add Event Receivers.

https://msdn.microsoft.com/en-us/library/office/jj245049.aspx .
POST http://<sitecollection>/<site>/_api/web/lists(listid)/eventReceivers

What is the bearer token it needs to attach ? I got OAuth token with all the permission for SharePoint online, Still I am not able to get the events if I attach event receivers by above POST call. Could anyone please point me, what Token it needs to attach event receivers, and how to get that token.